1*c8dee2aaSAndroid Build Coastguard Worker /* 2*c8dee2aaSAndroid Build Coastguard Worker * Copyright 2014 Google Inc. 3*c8dee2aaSAndroid Build Coastguard Worker * 4*c8dee2aaSAndroid Build Coastguard Worker * Use of this source code is governed by a BSD-style license that can be 5*c8dee2aaSAndroid Build Coastguard Worker * found in the LICENSE file. 6*c8dee2aaSAndroid Build Coastguard Worker */ 7*c8dee2aaSAndroid Build Coastguard Worker 8*c8dee2aaSAndroid Build Coastguard Worker #ifndef SkMatrix22_DEFINED 9*c8dee2aaSAndroid Build Coastguard Worker #define SkMatrix22_DEFINED 10*c8dee2aaSAndroid Build Coastguard Worker 11*c8dee2aaSAndroid Build Coastguard Worker #include "include/core/SkPoint.h" 12*c8dee2aaSAndroid Build Coastguard Worker 13*c8dee2aaSAndroid Build Coastguard Worker class SkMatrix; 14*c8dee2aaSAndroid Build Coastguard Worker 15*c8dee2aaSAndroid Build Coastguard Worker /** Find the Givens matrix G, which is the rotational matrix 16*c8dee2aaSAndroid Build Coastguard Worker * that rotates the vector h to the positive hoizontal axis. 17*c8dee2aaSAndroid Build Coastguard Worker * G * h = [hypot(h), 0] 18*c8dee2aaSAndroid Build Coastguard Worker * 19*c8dee2aaSAndroid Build Coastguard Worker * This is equivalent to 20*c8dee2aaSAndroid Build Coastguard Worker * 21*c8dee2aaSAndroid Build Coastguard Worker * SkScalar r = h.length(); 22*c8dee2aaSAndroid Build Coastguard Worker * SkScalar r_inv = r ? SkScalarInvert(r) : 0; 23*c8dee2aaSAndroid Build Coastguard Worker * h.scale(r_inv); 24*c8dee2aaSAndroid Build Coastguard Worker * G->setSinCos(-h.fY, h.fX); 25*c8dee2aaSAndroid Build Coastguard Worker * 26*c8dee2aaSAndroid Build Coastguard Worker * but has better numerical stability by using (partial) hypot, 27*c8dee2aaSAndroid Build Coastguard Worker * and saves a multiply by not computing r. 28*c8dee2aaSAndroid Build Coastguard Worker */ 29*c8dee2aaSAndroid Build Coastguard Worker void SkComputeGivensRotation(const SkVector& h, SkMatrix* G); 30*c8dee2aaSAndroid Build Coastguard Worker 31*c8dee2aaSAndroid Build Coastguard Worker #endif 32